; ------- lib ------------

(def != (a b) () (if (= a b) 0 1))
(def >= (a b) () (if (< a b) 0 1))
(def and (a b) ()(if a b 0))
(def or (a b) () (if a 1 b))
(def not a () (if a 0 1))
(def nop () () 0)
(def print a () (sys 1 a))
(def printc c () (sys 2 c))
(def space () () (sys 2 32))
(def nl () () (sys 2 10))
(def exit () () (sys 13))

; print string
(def prints s ()
  (while (vec s 0)
    (do
    (printc (vec s 0))
    (set s (+ s 1)))))

	; test string equal
(def str= (s1 s2) (flag i c1 c2)
  (do
  (set flag 1)
  (set i 0)
  (while flag
    (do
    (set c1 (vec s1 i))
    (set c2 (vec s2 i))
    (if (!= c1 c2) (set flag 0)
    (if (= c1 0)   (set flag 0)
    (if (= c2 0)   (set flag 0))))
    (set i (+ i 1))))
  (and (= c1 0) (= c2 0))))

  ; check is string a number, no sign
(def isNumber s a
  (do
  (set a (vec s 0))
  (while (and (> a 47) (< a 58))	; isdigit a
    (do
    (set s (+ s 1))
    (set a (vec s 0))))
  (= a 0)))				; true if reach end


; ---------------------
(let tok)

(def tokenise () ()
  (set tok (sys 3)))

(def parseSym () ()
  (do
  (if (str= tok "ADD")
    (do
	(prints "OP:") (prints tok))
  (if (isNumber tok)
    (prints tok)
  ; else
	(do
	(prints "VAR:") (prints tok))))
  (space)))

(def parseX () () 0)		; forward declaration

(def parseL () ()
  (do
  (tokenise)
  (if (not (str= tok ")"))
    (do
	(parseX) (parseL)))))

(def parseX () ()
  (do
  (if (str= tok "(")		; it is a list
    (do
    (tokenise)
    (parseSym) (parseL))
	; else
    (parseSym))))

; ---------------------------

(def main () ()
  (do
  (sys 11)		; readinfile
  (tokenise)
  (parseX)))